Newbie - Tool Changes

I know this question has been asked in other places, but I am new at this and want to ask a little more directly.

How are people doing tool changes(one gcode file or multiple) and staying accurate on the next cut? Even with the motors engaged it is possible to shift things slightly off. A 1+mm can make a huge difference when trying to do a finishing cut.

I have tried to record my coordinates before zeroing my origin and the rehoming and dialing back in my coordinates, that can be ever so slightly off as well because of slight variations on the Y endstops.

Thanks in advance!

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I haven’t done it a lot. But I just separate the gcode into different gcode jobs and run them separately. I have seen a lot of clever gcode scripts in the forums. But I just prefer to keep it simple and do the tool change myself.


Here is my tool change script in Estlcam. All my tool changes happen in the same gcode so I can machine continuously.

;Change tool
M107 ; turn off spindle
G01 X0 Y0 Z5 F2000 ; Move to relative origin
M18 Z ; disable z stepper
M00 ; pause and wait until button press on LCD
G28 Z ; z probe
G92 Z0.5 ; account for probe thickness
G01 Z5 ; raise out of the way to remove probe
M00 ; pause for click to resume
M106 ; turn on spindle and continue

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i appreciate the quick responses. I am talking more about the physical change. Using the wrench, untightening the bit, maybe switching collets, tightening another bit, making sure the core doesnt shift at all during this process.

Yes, I do all of those things at this point:

  M00 ; pause and wait until button press on LCD

Right before this line you will see that the Z axis is disabled. This way you can move the Z axis up and down to remove your bit and install the new bit (collet too if needed). Notice this does not disable the X and Y axis. This way your tool/router is still fixed to the same XY coordinate system. Once the new bit is installed you need to attach the z probe to the bit then you click the button on your LCD screen and it will start the z probe. Once the probe is complete, it will pause and ask you to press the button again. Before you press the button be sure to remove the probe. When you press the button, it will resume the machining process with your new bit installed. The X and Y coordinates are preserved the entire time, and you get a new Z coordinate with the probe.

Is this what you are looking for?

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For an LR3, it shouldn’t be. At least not in x and y.

I take the router out completely to change the bit. But I don’t use a script. Matt’s script and advice is for an MPCNC. You don’t want to disable the Z motors for an LR and the G28 Z is for an MPCNC.


Oh yeah mine is for MPCNC, I see now you are using a LR. But I would think you could apply a similar process for the LR. Instead of disabling the Z, just have it raise to its maximum position to give you the most room possible. You can even remove the router like Jeff mentioned. And then whatever command the LR requires for probing.

Maybe this is the answer, maybe the motors should be holding better than they are. They aren’t super loose, but i still have to be very careful not to shift the gantry in one direction or another. you can move those motors even when they are on. i havent had any issues, so i am not sure what would be causing this.

I don’t have a LR, so I am not familiar with its holding power. The MPCNC uses two motors per axis (one each side) so its holding power is quite high. I would break something before I get an axis to move while engaged. I believe there is just the one stepper per axis on the LR, correct?

If there is an issue with you shifting the gantry while using the wrench, they maybe removing the router for the tool change is the best way.

The LR has two Y, two Z, one X.

I don’t want to move it either, so I am careful about removing the router. I can definitely make any of the axis skip steps, but (I don’t want to brag) I am also the go-to person in the house to open stuck jars.

As long as there isn’t anything really wrong (like a loose grub screw, a broken belt reinforcement, a cracked part, a loose wire), you could try increasing the stepper driver current. Keep an eye on the temp of the motors and the temp of the drivers. 50mA can be a big difference.

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that is a good idea. i may try that. Also going to take a look at the power piece.

I do this quite often, even with tiny inlays, and it’s never been a problem as long as the motors are still on. Estlcam pauses the job, lets me jog the router wherever I want to change and then continues where it left of. You can see it in a few of my videos.

Looking a little closer, i actually think i may have figured it out. I tightened my belts more and it has made it a lot more rigid. I haven’t had any issues cutting and didn’t really know how tight to make them, especially since its been working. They weren’t loose by any means, but weren’t firm. I am going to do some tests and try this. Thanks for all the replies!

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You can test the belt tension really well when doing boxes with fingerjoints. If the joints fit, your belts are doing good, if they are off by a mm or so, you have to tighten the belts. Don’t ask me how I know… :stuck_out_tongue:

I agree with you there! All my jobs are broken down into different gcode for each bit. It allows large jobs to have a stopping point when work or life gets in the way. The material is set up at the machine origin so if there is a day or two in between cuts, simply home the machine (actually set x&y home +10mm) and start cutting again. It has been foolproof for me.

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